This invention relates to a fiber reinforced structural material. In a more specific aspect, this invention concerns itself with a ceramic composite comprised of high strength alumina fibers in a glass matrix.
The present interest in the utilization of lasers has created a need for structural materials that are especially resistant to the degradation and damage resulting to structural entities when exposed to laser energy. These materials must also possess structural strength and stability in conjunction with a high temperature operating capability.
Fiber reinforced organic matrix composites are widely used and accepted as structural materials because of their desirable attributes of high strength, high moduli and low density. In general, most of these composites possess an organic polymer matrix, such as an epoxy resin, a polyimide, a polycarbonate or similar material. The matrices are reinforced with a great variety of fibers including glass, carbon, graphite and boron. However, even the best of these materials are limited to an operational temperature environment below 300.degree. F. The substitution of a metallic material, such as aluminum for the organic matrix, extends the operational temperature range only slightly. The need for a composite structural material, therefore, that possesses a high temperature operational capability in conjunction with resistance to laser damage, therefore, becomes obviously when one perceives the tremendous strains and stresses encountered by structural materials used in modern day high speed aircraft and missiles.
The utilization of a glass composition for producing fiber reinforced glass composites is disclosed in U.S. Pat. No. 3,607,608 to Siefert wherein the fibers are produced by pulling the fibers through a molten glass bath and then through a constricting orifice. The resulting composites exhibit high strength and no loss in properties after exposure to 540.degree. C. for 100 hour. Siefert, in U.S. Pat. No. 3,792,955, also discloses glass composites with molybednum, tungsten and boron as the reinforcing fiber component. These fibers also show stability after exposure to a temperature of 540.degree. C. for 100 hours. These materials, however, do not disclose a high resistance to laser damage nor are they known to be capable of operating in a temperature environment of from 600.degree. to 1100.degree. C. in the same manner as the all ceramic, alumina and glass, composite system of this invention.